In recent years, in order to secure a large amount of displacement in an small piezoelectric actuator under a high pressure, a strong electric field has been applied to the piezoelectric actuator and it has been continuously driven or a long period.
In a laminated-type piezoelectric element utilized in such a piezoelectric actuator, when it has been continuously driven under a strong electric field and a high pressure for a long period, external electrodes for a positive electrode and a negative electrode disposed at side areas of the laminated-type piezoelectric element cannot follow movements of expansion and contraction of the laminated-type piezoelectric element. Therefore, peeling occurs between the internal electrode formed between piezoelectric bodies and the external electrode, or a crack occurs at the external electrode and the external electrode breaks. Thereby, a problem occurs where an electric voltage is not supplied to a part of the piezoelectric body, and the displacement properties change during driving.
Therefore, Japanese unexamined patent publication No. 8-242025 proposes a laminated-type piezoelectric element wherein a thin sheet of an electrically conductive material, where a notch was formed in a width direction, is connected to a side area of the laminated-type piezoelectric element with an electrically conductive adhesive so as to make the thin sheet of an electrically conductive material electrically continuous with an internal electrode.